I know many companies that do select whole teams, but it's also cleaning house time and the lowest performer from a previously non-impacted team will be included as laying off is easier than firing depending on where in the world you are.

Regardless, in absence of information, you cannot conclude that someone who was laid off was an underperformer. It can just as well be a member of a team who was considered lower-priority and disbanded.

He's describing a general bias that absolutely exists, whether it's always accurate is unrelated.

Fair enough.

If you're laying off people, you're going to also get rid of the low performers. Maybe you don't have enough low performers (or just don't know who they are) to make up the quota and you have to remove whole teams or use arbitrary metrics, but there will be an overrepresentation of below-average workers compared to the survivors. Source: wife is a manager at a company that had single-digit percent layoffs.